Trawling device



July 19, 1960 o. B. PULSIFER TRAWLING DEVICE 2 Sheets-Sheet 1 Filed Jan. 27, 1958 uly 19, 1960 o s. PULSIFER 2,945,469

TRAWLING DEVICE Filed Jan. 27, 1958 2 Sheets-Sheet 2 BYJW A rraemsrs.

TRAWLING DEVICE Orville B. Pulsifer, 207 Roy Bldg., P.0. Box 911, Halifax, Nova Scotia, Canada Filed Jan. 27, 1958, Ser. No. 711,274

3 Claims. (Cl. 114235) This invention relates to a control device for automatically controlling the depth at which an object is towed in water and is concerned particularly with control of the depth at which a fishing net is trawled.

In the field of trawl fishing wherein nets are towed at a depth behind a trawling vessel there is a requirement to maintain the depth at which the nets are trawled constant and at a specified level. This requirement led to the development of many devices to lower the net to a specified depth and maintain it at that depth during the trawling operation. One such device is the trawling otter board which is mounted on the tow line and by means of a planing action tends to pull the net into the water. The otter board is dependent for its operation on the forward motion of the trawling vessel. Hence the more rapidly the trawling vessel moves, the deeper the net is sunk and conversely, if the trawler moves slowly, the net will tend to rise to the surface. The nets being trawled also have a variable buoyancy due to the contents, i.e., the accumulation of fish, etc., during the trawling operation which may modify the action of the otter board. An improvement on the otter board which is in common use is the addition of weights to the tow line as an .aid in sinking the net. This arrangement also suffers from the disadvantage that the depth at which the net is trawled is dependent upon the forward speed of the trawling vessel.

Various types of adjustable planes have been attached to configurations of otter boards in order to control the depth at which the otter board operates. However, these devices have all either been of the preset kind wherein the relative angle which the variable planer makes with the forward motion of the otter board is fixed prior to placing the otter board in the water or else a device which is controlled trcm the trawling vessel by means of mechanical linkages. These adjustable elements in practice have not proved satisfactory since the preset trawling board with variable planes offers little, if any, improve ment over the standard trawling otter board. The otter board which has variable vanes controlled from the trawling vessel requires complex mechanical linkages to control the setting of the plane and to indicate the depth at which the otter is being trawled. These mechanical linkages interfere with the operation of setting or reeling in the trawling nets. Otter boards in themselves are awkward to handle and diflicult to launch or bring back into the trawling vessel.

The present invention overcomes the deficiencies of the prior devices used for regulating the depth of nets in trawl fishing by providing automatic control of the depth to which the net is lowered, the depth of trawling being independent of the forward velocity of the trawling vessel or variations in buoyancy of the net being trawled. The

present invention is also convenient to handle and may be readily launched or returned to the trawling vessel.

According to the present invention a draw-bar is inserted between the trawling line from the trawling vessel and the tow line to the net. The draw-bar is ates Patent assumes a position which tends to draw the net down to the desired depth. On reaching the desired depth, the control hydrofoils neutralize their position and operate to maintain the net at the desired depth. The hydrostatic control device is preset prior to launching of the mechanism and maintains the net at the specified depth during the entire trawl operation regardless of the buoyancy of the net. It may thus be seen that no external controls are required and that the depth to which the net is lowered is independent of the variation and forward motion of the trawler, variations in ocean currents, or buoyancy of the net.

In the drawings which illustrate embodiments of the invention,

Figure 1 is a plan view of the apparatus according to the invention,

Figure 2 is a side elevation of the apparatus,

Figure 3 is a side elevation of the hydrostatic control element, and

Figure 4 is a perspective view of the apparatus according to the invention.

The embodiment of the invention illustrated in Figure 1 comprises a draw-bar 10 with a shackle 30 coupled to the forward end and a shackle 31 coupled to the rear end thereof, the shackle 30 provides connection to the trawl line of the trawling vessel and the shackle 31 pro vides connection to the tow line for the trawl net.

Through the forward portion of the draw-bar 10 a nylon bearing 16 is fitted and inside this nylon bearing a tube 24 is fixed. Mounted to either end of this tube 24 are the main hydrofoils 22a and 22b. At the rear outer extremities of the main hydrofoil 22a, 22b are mounted horizontal stabilizers 14a and 14b respectively. Side body members 23a and 23b are fixed to main hydrofoils 22a and 22b respectively. At the rear extremity of horizontal side members 23a and 23b are attached control hydrofoils 25a and 25b respectively. Supporting rods 26a and 26b are fastened at their for-ward ends to side body members 2311 and 23b respectively, and at their rear ends to support elements 27a and 27b respectively which in turn are fastened to the rear upper and lower portions of side body members 23a and 23b respectively.

Hydrostatic control cylinder 11 is mounted in the body of main hydrofoil 22a and is coupled by crank 32 to pivot rod 13. Control rods 28a and 28b are connected to cranks mounted on pivot rod 13 at one extremity and to cranks 33, 34 attached to elevator planes 25a and 25b at their other extremities.

Air balance tank 29 which is mounted in main hydrofoil 22b is connected via tubing 20 to hydrostatic cylinder 11. Depth gauge 12 is a pressure gauge calibrated in equivalent depth in fathoms.

Figure 2 is aside elevation of the present invention which illustrates the possible radius of action of the draw bar 10 with respect to the main body of the invention 23. Rubber stops 15 are fitted to the upper and lower rear extremities of body 23a and b to limit the motion of draw-bar 10. This limit of motion facilitates recovery and launching of the mechanism and enables the present invention to be readily raised from the water.

Static pendulum balance 35 which operates to maintain the main hydrofoils 22a and 22b level in the water is connected by means of linkages (not shown) to horizontal stabilizers 14a and 14b.

In operation the air balance tank 29 is filled with compressed up to a pressure which will correspond to thedepth .to..which the trawling device is to be lowered, this depth being indicated on the depth gauge 12. This air pressure is also transmitted to the cylinder 11 Fig. .3) iandinflatesnthe :nubber rbladder 40 which exerts a frce,-agaiI St -piston-{i1. spring loaded against-pad Q2 byte means no sh w is cra -a m fl hi QQ ne e ta q 1 (Pia. by means of i rank- VCQ ,tr0l;bar;28is, connected to element 13 atone endand atstherother endtoelevator hydrofoil l5 by meansi of another. ra k' Wh h IaW d ice pla e i the water the elevator plane assumes a position which tends t a r l h ameeha ism downwar unt a dept is reached wh rethep es u e act n o t etopp h -P1' t0n;41; is. equa to th p s ur t bl dde 0. a the ,pistonA-Lsinks intothe cylinder 39. From Figure 2 itU-m v-he-se .thatasth pi t md sce ds int th cylinder .9, cran :32 is t tated 9 kw ,;=e1em a s rotate rcl c twis wh icause b ,2. o bem cdto therightiandie evatoriplan l aa sr r e t a aeut position- I th nappa atn d sc d vt aep te than that for which the device has been set, a,fur ther ele ky seimot o ao cran .w l r su e u n Plane 25a to be rotated anti-clockwise which will vexert a ters vno he main-med) .of h inve io to ur it to a shallower depth.

As p v nu lyrm nti ne ,mepresent invention is runa fe te nby sva ia on n buoya y of he net being trawled. Additionally, the present invention giyesjmproved operation with increase in speed of the trawling vessel, and will maintain depth more accurately \withsuch an in r a ezintspe ;What I claimflas my invention is:

;1. Apparatus ,for controlling the depth at which an object isatowed in water, comprising .a draw.-bar..adapted to connectubetween a.tow cable and an object to be .tQWed, (aimain framespivotally. connected to said draw- -har ,adja centthe end.adapted to be connected to the .tow

cable and, extending on.either.side. of said draw-bar, a 'paintofnmain:hydrofoils rigidly attached to said main frame adjacent the connection of said main frame to said tire -ba tae esteqine Vqutwardly t a frame on either side of said draw-bar, stabilizing means comprising roll control means mounted on the main hydrofoils and roll-deviation sensing means operatively connected to said control means for stabilizing the main hydrofoils in substantially horizontal planes during towing of the apparatus, a pair of eleyatorplanes mounted on either side of said main frame at th e endthereof remote from said main hydrofoils, and hydrostatic elevator control p tene etiye estimate wsai ele t P a e and adapted to cggti ol said e levator planes thereby to control the deptlrat which said apparatus is towed.

2. Apparatus as claimed. in claim-i, wherein said bydrostatic control rneansmpmprises ,a compressed air tank, a cylinder, a piston slidably fitted within said cylinder, one end of said cylinder being subject to pressure of the water in which said object is towed and the other es ein t bi, t P qm ewm e e air tea ai vpis e be n ada e t be r nsiv i its PP t Q -W thi h t vl nd t th -di r nt a n P3 sure between the two endspf the cylinder; vand mechanil elsese r pna ste .toai P n a a l p t pstat ei e vet n a m r ne ,-3- -A 11.ar tu =-a l ime in. c aim I 1, wh e Said. zqe etiq seasi am eqm r s ulu e p sivei to deviations and said roll control means coinpr is ra re ii r qnta s abili e planes mq j te near-th s em tie flsei e r tq l an l n be we sa p nd um and ho z a S abi Pl ad te to oee e sa vhqr zqnta s ebi iz Plane i e pqns .t em temen p th Qendulu t st b zes i :Burney Nov. 9, 1920 ,Fryklund Ian. 10, 1956 

